Hydraulic classifier



Jan. 17, 1956 K. KREBS 2,731,147

' HYDRAULIC CLASS IFIER Filed April 24, 1953 ATTORNE Y5 United States Patent HYDRAULIC CLASSIFIER Kellogg Krebs, Palo Alto, Calif., assignor to Equipment Engineers, Inc., San Francisco, Calif., a corporation of California Application April 24, 1953, Serial No. 351,006

5 Claims. (Cl. 209-211) This invention relates generally to hydraulic classifying or separating methods and to apparatus for carrying out such methods.

Various types of centrifugal methods and apparatus have been employed for classifying or removing suspended solids from hydrous slurries. One simple type which has been used to advantage in many industrial operations employs a stationary chamber having a lower provision for separately removing centrifugally separated overflow and underflow fractions. Slurry is introduced tangentially into the upper part of the chamber from a pump or like pressure source, whereby the entire body of liquid within the chamber rotates about the vertical axis of the same to thereby develop centrifugal separating forces. The overflow is established through a conduit which communicates with the central part of the chamber, and which has a circular or annular inlet opening. With given equipment of this type, operating under fixed conditions, the diameter of the inlet end of the overflow conduit imposes a flow restriction on the system whereby a certain static pressure must be established within the chamber to obtain a desired flow capacity. In other words such apparatus always involves a pressure drop in a closed system in which it is installed. If it is attempted to increase the capacity of the equipment, or its separating efliciency, by a higher rate of flow of slurry to the chamber, the pressure drop increases and may become excessive. Thus apparatus of this kind when designed for particular separating or classifying operations, are limited as to flow rate and capacity.

In general it is an object of the present invention to provide simple separating or classifying apparatus capable of overcoming the inherent limitations referred to above. The present invention makes possible a relatively high capacity for a given size of apparatus, and without sacrifice in power consumption or separating efficiency.

Further objects and features of the invention will appear from the following description in which the preferred embodiment of the invention has been set forth in detail in conjunction with the accompanying drawing.

Referring to the dawing:

Figure 1 is a side elevational view, partly in section, illustrating apparatus incorporating the present invention.

Figure 2 is a cross sectional view taken on the line 22 of Figure 1.

The method of the present invention can be best understood after describing the apparatus illustrated in the drawing. This apparatus consists of a housing which is annular in section, and which is disposed with its central axis in a vertical position. The lower portion 11 of the housing is conical shaped, while the upper portion 12 is substantially cyindrical. In order to facilitate manufacture the upper part of the housing includes the extension 13 which is annular in section, and of substantially the same internal diameter as the housing part 12. The housing part 12 is shown provided with the flange 14, which is secured to the top plate 15 by clamping bolts 16, whereby the housing extension 13 is firmly clamped ice between the top plate 15 and the upper end of the housing part 12. A part 17 is secured to or may be formed integral with the main part of the housing extension 13 and provides an inlet flow passage 18 which communicates tangentially with the interior of the housing. Piping 19 which may lead from a slurry pump or other source of slurry under pressure, is shown coupled to the part 17 by the pipe coupling section 20, the latter providing a passage of gradually reduced cross-sectional flow area.

The interior 21 of the housing forms a treatment chamber in which material rotates about the central vertical axis of the housing whereby solids of the slurry are subjected to centrifugal separating forces. At the lower end of the conical housing part 11 provision is made for the continuous or intermittent removal of heavier separated underflow material. Thus the lower end of the conical part 11 is shown connected to a short pipe section 22, which in turn connects with the underflow withdrawal pipe 23. Flow of material through this pipe can be controlled by a suitable adjustable orifice or valve 24.

Centrifugally separated overflow is withdrawn from a centralized region 26 of the chamber 21. For this purpose I provide two withdrawal pipes or conduits 27 and 28, which have vertically spaced and opposed inlet openings 29 and 31. Conduit 27 extends outwardly and is secured to the exterior coupler 32, which in turn connects with the exterior pipe 33. Conduit 28 extends downwardly through the pipe section 22, and is secured at its lower end to the exterior coupling 34, the latter communicating with the exterior pipe 36. It will be noted from Figure 1 that the passages provided within the conduits 27 and 23 are divergent.

The spacing between the inlet openings 29 and 31 should be suflicient to avoid any substantial amount of turbulence in the region 26, due to flow of materials through these openings. Good results have been secured by using a spacing equal to about four times the diameter of the openings.

Operation of the apparatus as described above, and the steps of my method are as follows: A hydrous slurry is continuously supplied to the housing 10 through the piping 19. In a typical installation a centrifugal pump is used for this purpose and is capable of maintaining a hydraulic pressure head of the order of from 10 to 70 p. s. i. The slurry is thus discharged through the passage 18 into the upper part of the chamber 21 with considerable velocity. The chamber 21 is maintained filled with material undergoing treatment. The'kinetic energy of the material discharging from passage 18 causes the entire body of material within the chamber to rotate aboutits vertical axis. The angular velocity of material in the rotating mass increases toward the central axis. Such rotation causes centrifugal separating forces to be applied to the heavier solids of the slurry, thus causing these solids to progress outwardly and then downwardly into the conical portion 11. Ultimately solids accumulate in the pipe coupling 22 and are removed continuously through the pipe 23 and valve 24. An overflow discharges continuously through the conduits 27 and 28 and may be collected at the discharge ends of the pipes 33 and 36. Since the inlet openings 29 and 31 of conduits 27 and 28 are of the same diameter and are aligned on a common vertical axis, the characteristics of the two overflow streams are the same. Furthermore the spacing between the inlet openings is such that no substantial amount of turbulence is caused in the region 26, due to flow of material through the openings 29 and 31, and such as might interfere with maintaining a sharp separation. The region 26, with which the openings 29 and 31 communicate, is located intermediate the ends of the housing whereby it is in the central orbit or maximum of centrifugal separating forces; and it is in this region that the angular velocity (i. e. R. P. M.) of the material reaches its maximum value. Below the opening 31 the speeds of rotation gradually decrease, due to friction against the inner surfaces of the side walls.

With the apparatus and method described above, it is possible to maintain an optimum speed of rotation within the housing, and about the region 26, due to flow through both the outlet openings 29 and 31. This is because a relatively high fiow capacity can be provided by the two outlet openings 29 and 31, for a given effective diameter. It will be evident that this is a highly advantageous feature because as the diameter of an overflow outlet is increased, the sharpness of separation is necessarily materially impaired.

As an example of actual practice makinguse of the present invention, in one instance the housing had an internal diameter of inches and in inflow passage 18 about 1.4 inches in diameter. The proportioning of the housing was generally in accordance with the present drawing. The openings 29 and 31 each measured 1 inch in diameter, and were spaced 4 inches apart. Opening 29 was located 4 inches below the top plate 15. This apparatus was used to classify a hydrous slurry containing 36% suspended solids. These solids were largely silica and clay. All of the solids of the slurry were minus 65 mesh, with 67.2% of the solids minus 325 mesh. This slurry was put through the apparatus at the feed rate of 65 gallons per minute. The results obtained were tabulated as follows:

Per cent Feed percent solids 36.0 Feed percent +325 32.8 Feed percent 325 67.2 Overflow percent solids 21.6 Overflow percent +325 Nil Overflow percent '325 100.0

Underfiow percent solids 72.5 Underflow percent +325 59.5 Underflow percent 325 40.5 Percent +325 into overflow 67.0

It will be apparent from the above tabulated data that my invention makes possible high capacity and a relatively sharp separation between solids having different separating characteristics. The results obtained are markedly superior to other types of separating equipment such as previously described, which make use of a single overflow discharge conduit.

1 claim:

1. In hydraulic classifying apparatus, a stationary vertical chamber annular in section, the lower portion of said chamber being conical shaped, means for introducing hydrous slurry to be classified into the upper portion of said chamber and tangentially, and means for removing overflow material from a region located axially of the chamber and intermediate the end thereof, said last means including two conduits axially aligned with the ,axis of the chamber and having oppositely faced annular inlet ends, of substantially the same diameter.

2. Apparatus as in claim 1 in which said ducts communicate with a region located generally within that part of the chamber surrounded by the upper end of the conical shaped portion.

3. In hydraulic classifying apparatus for the handling of hydrous slurries containing solids to be separated, .a vertical chamber annular in section, the chamber being formed with a lower depending conical shaped portion, means for continuously introducing a feed of hydrous slurry tangentially into the upper portion of the chamber, whereby the body of material in the chamber is caused to rotate about the axis of the chamber, means communicating with the lower end of the chamber for the removal of centrifugally separated underflow solids, and means for continuously removing overflow from a :region located on the axis of the chamber and intermediate the upper and lower ends of the chamber, said last means comprising a pair of conduits aligned with the axis of the chamber and having opposed spaced annular inlet ends, said inlet ends of the conduits being located above and below the region from which the overflow is withdrawn, the inlet ends of said .ducts being annular in section and'of substantially the same diameter.

4. Apparatus as in claim 3 in which said conduits extend to the exterior of the chamber through the upper and :lower ends thereof.

5. In hydraulic classifying apparatus for the handling of hydrous slurries containing solids to be separated, a vertical chamber annular in section, means for continuously introducing afeed of hydrous slurry into the upper portion of the chamber whereby the body of material in .the chamber is caused to rotate about the axis of the chamber, means communicating with the lower portion of the chamber for the removal of a centrifugally separated underflow, and means for continuously removing overflow from a region located on the axis of the chamber and intermediate the upper and lower ends of the chamber, said last means comprising a pair of conduits aligned with the axis of the chamber and having opposed spaced annular inlet ends, said inlet ends of the conduits being located above and below the region from which theoverflow is withdrawn, the inlet ends of the said ducts being annular in section and of substantially the same diameter.

References Cited in the file of this patent UNITED STATES PATENTS 474,490 Walter May 10, 1892 1,845,566 Stebbins Feb. 16, 1932 2,098,608 Berges Nov. 9, 1937 

1. IN HYDRAULIC CLASSIFYING APPARATUS, A STATIONARY VERTICAL CHAMBER ANNULAR IN SECTION, THE LOWER PORTION OF SAID CHAMBER BEING CONICAL SHAPED, MEANS FOR INTRODUCING HYDROUS SLURRY TO BE CLASSIFIED INTO THE UPPER PORTION OF SAID CHAMBER AND TANGENTIALLY, AND MEANS FOR REMOVING OVERFLOW MATERIAL FROM A REGION LOCATED AXIALLY OF THE CHAMBER AND INTERMEDIATE THE END THEREOF, SAID LAST MEANS INCLUDING TWO CONDUITS AXIALLY ALIGNED WITH THE AXIS OF THE CHAMBER AND HAVING OPPOSITELY FACED ANNULAR INLET ENDS, OF SUBSTANTIALLY THE SAME DIAMETER. 